Medical imaging apparatus with accurate patient postioning

ABSTRACT

A medical imaging apparatus in which an easy and accurate positioning of an imaging target inside a patient within a view field of an imaging device is possible. The apparatus includes: a signal detector for collecting the image data, having a limited effective view field located inside a frame; a carrier for carrying the patient into the frame in order to place the imaging target portion of the patient within the effective view field of the signal detector; and an indication marking, attached on the carrier, for indicating a range on the carrier which can be located within the effective view field of the signal detector. The apparatus may further includes: a height adjustment device for adjusting a height of the carrier by moving the carrier in a vertical direction; and a height indicator for indicating the height of the carrier on a scale provided on a horizontal plane so as to provide an easily and accurately readable indication of the height of the carrier.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical imaging apparatus, such as aSPECT (Single Photon Emission Computed Tomography) apparatus, an X-rayCT (Computed Tomography) apparatus, and a gamma camera apparatus, inwhich a patient on a bed is positioned inside an imaging space definedby a view field of a signal detector for collecting imaging signals tobe reconstructed into the images by using signal processing.

2. Description of the Background Art

One example of a conventional medical imaging apparatus is a SPECTapparatus which is a type of a gamma camera apparatus in which a gammacamera for detecting gamma rays through a fan beam collimator from apatient is provided around the patient to which an injection containinga radioactive isotope (RI) had been given, and fan beam tomographicimage data for reconstructing tomographic images by using signalprocessings are collected by rotating the gamma camera around thepatient for 360°. The gamma camera of such a SPECT apparatus has atwo-dimensional detection capability so that multi-slice tomographicimages can be obtained from a single 360° rotation of the gamma camera.

An exemplary configuration of such a conventional SPECT apparatus isshown in FIG. 1, where the SPECT apparatus generally comprises: a bed 6for carrying a lying patient 9 with a head portion 9a supported by ahead rest 1; and a frame 4 having a cylindrical bore 5 into which thepatient 9 on the bed 6 is positioned by moving in a horizontal Xdirection, and a gamma camera 2 capable of rotating 360° around acircumference of the cylindrical bore 5 to collect the tomographic imagedata. The gamma camera 2 has an effective view field vf in the Xdirection which is narrower than its full width, and is capable ofcollecting tomographic image data only within this effective view fieldvf. The collected tomographic image data are subsequently reconstructedinto the multi-slice tomographic images by using the signal processings,and the reconstructed tomographic images are displayed on a displaydevice for medical diagnostic use. Here, the tomographic images cancover only those regions of the patient which are located within theeffective view field vf of the gamma camera 2.

Such a SPECT apparatus has increasing demands because it is more usefulin the diagnosis of a head portion and a heart portion compared withother diagnostic devices.

However, such a conventional SPECT apparatus has been associated with aproblem that an accurate positioning of a target region of the patientwithin the effective view field vf of the gamma camera 2 has beendifficult such that a re-positioning of the patient in the cylindricalbore 5 has often been necessary. This is due to the fact that a simpleway of ascertain a correct positioning of the patient before thepositioning of the patient inside the cylindrical bore 5 has not beenavailable in a conventional SPECT apparatus such that the positioning ofthe patient has been depending on an experienced guess of an operatorwhich may not necessarily be so reliable. Thus, the operator of aconventional SPECT apparatus has been required to put up with frequentand cumbersome repositioning of the patient.

Moreover, as already mentioned above, the SPECT apparatus is employedmostly for the diagnosis of the head portion of the patient, so that acapability for an easy and accurate positioning of a small and invisiblepart of the head portion of the patient is an important requirement inview of a maneuverability of the apparatus. For example, as shown inFIG. 2, a cerebellum portion 11 inside the head portion 9a of thepatient 9 has been difficult to position accurately within the effectiveview field vf of the gamma camera 2 by a single patient positioningoperation in a conventional SPECT apparatus.

Another example of a conventional medical imaging apparatus is an X-rayCT apparatus which has a typical configuration as shown in FIGS. 3 and4.

This X-ray CT apparatus generally comprises: a bed 31 for carrying alying patient 33, including a carrier plate 36 for moving the patient 33in a horizontal X direction and a height adjustment unit 37 foradjusting a height of the carrier plate 36 in a vertical Z direction;and a frame 32 having a cylindrical bore 38 into which the patient 33 onthe bed 31 is positioned by moving the carrier plate 36 in thehorizontal X direction, an X-ray imaging unit including an X-ray tube 34and a detector 35 which are capable of rotating 360° around acircumference of the cylindrical bore 38 to collect the tomographicimage data.

As shown in FIG. 4, the X-ray tube 34 and the detector 35 are located atopposing positions on a slicing plane SP, and are rotated together onthis slicing place SP around the patient 33 positioned inside thecylindrical bore 38 during the imaging process.

Now, in such a conventional X-ray CT apparatus, the height of thecarrier plate 36 is made to be adjustable by means of the heightadjustment unit 37 such that the apparatus can be adjusted to a patientof any physical size.

In adjusting the height of the carrier plate 36 by using the heightadjustment unit 37, it is necessary to provide a height indicator forindicating a present height of the carrier plate 36 to an operator.

Conventionally, such a height indicator has been provided as shown inFIGS. 5(A) and 5(B). Namely, the height adjustment unit 37 of FIGS. 5(A)and 5(B) comprises: a fixed lower frame 51 fixed to the floor; a movableupper frame 52 on which the carrier table 36 is mounted and which iscapable of moving in the vertical Z direction with respect to the fixedlower frame 51 by being driven by a power source (not shown); a scale 53attached on a side of the fixed lower frame 51 along the vertical Zdirection; and a pointer 54 attached on the same side of the movableupper frame 52 along the scale 53 which points a marking on the scale 53corresponding to the height of the carrier plate 36 which can be readoff by the operator.

However, in this configuration of the height adjustment unit 37 of FIGS.5(A) and 5(B), the scale 53 is located at such a position that theoperator has to bend down in order to read off the scale readingcorrectly, so that the reading operation is cumbersome. Also, in thisconfiguration, a range of the adjustable heights for the carrier plate36 is limited by a size of the scale 53, so that it has been difficultto lower the carrier plate 36 as low as considered preferable by manyoperators nowadays.

Alternatively, a height indicator can also be provided as shown in FIGS.6(A) and 6(B). Namely, the height adjustment unit 37 of FIGS. 6(A) and6(B) comprises: a base frame 61 fixed to the floor; a movable frame 62on which the carrier table 36 is mounted and which is capable of movingin the vertical Z direction with respect to the fixed lower frame 61 bybeing driven by a power source (not shown); a wire 64 suspended from themovable frame 62 in the vertical Z direction; a position detector 65such as an encoder or a potentiometer which is attached on the wire 64and measuring a length of the wire 64 corresponding to the height of thecarrier plate 36; a drum 66 for rolling up or down the wire 64 as themovable frame 62 is lowered or raised; and a digital indicator using LEDfor indicating the height of the carrier plate 36 measured by theposition detector 65 which is located on a side of the movable frame 62,such that the indication of the height can be read off easily andaccurately.

However, in this configuration of the height adjustment unit 37 of FIGS.6(A) and 6(B), numerous additional electronic components are required,so that the configuration of the height adjustment unit 37 becomescomplicated and the apparatus inevitably becomes more expensive.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a medicalimaging apparatus in which an easy and accurate positioning of animaging target inside a patient within a view field of an imaging deviceis possible.

It is also an object of the present invention to provide a medicalimaging apparatus in which the indication of the height of the carrierplate can be read off easily and accurately without a complicatedconfiguration and an increased cost.

According to one aspect of the present invention there is provided amedical imaging apparatus for obtaining images of an imaging targetportion of a patient from image data collected from the patient,comprising: signal detector means for collecting the image data, havinga limited effective view field located inside a frame; carrier means forcarrying the patient into the frame in order to place the imaging targetportion of the patient within the effective view field of the signaldetector means; and indication marking means, attached on the carriermeans, for indicating a range on the carrier means which can be locatedwithin the effective view field of the signal detector means.

According to another aspect of the present invention there is provided amedical imaging apparatus for obtaining images of an imaging targetportion of a patient from image data collected from the patient,comprising: signal detector means for collecting the image data, havinga limited effective view field located inside a frame; carrier means forcarrying the patient into the frame in order to place the imaging targetportion of the patient within the effective view field of the signaldetector means; height adjustment means for adjusting a height of thecarrier means by moving the carrier means in a vertical direction; andheight indicator means for indicating the height of the carrier meansadjusted by the height adjustment means on a scale provided on ahorizontal plane.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example of a conventional SPECTapparatus.

FIG. 2 is a schematic diagram for explaining the positioning of apatient in the conventional SPECT apparatus of FIG. 1

FIG. 3 is a schematic perspective view of an example of a conventionalX-ray CT apparatus.

FIG. 4 is a schematic diagram of the conventional X-ray CT apparatus ofFIG. 3.

FIGS. 5(A) and 5(B) are a front view and a partial side view,respectively, of one example of a height adjustment unit in theconventional X-ray CT apparatus of FIG. 3.

FIGS. 6(A) and 6(B) are a front view and a partial side view of anotherexample of a height adjustment unit in the conventional X-ray CTapparatus of FIG. 3.

FIG. 7 is a schematic diagram of the first embodiment of a medicalimaging apparatus according to the present invention.

FIG. 8 is a schematic diagram of the second embodiment of a medicalimaging apparatus according to the present invention.

FIGS. 9(A) and 9(B) are a side view and a front view, respectively, ofthe first embodiment of a bed for a medical imaging apparatus accordingto the present invention.

FIGS. 10(A), 10(B), and 10(C) are a top plan view, a front view, and aside view, respectively, of a main part of the bed of FIGS. 9(A) and9(B).

FIGS. 11(A) and 11(B) are a side view and a front view, respectively, ofthe second embodiment of a bed for a medical imaging apparatus accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 7, a first embodiment of a medical imagingapparatus according to the present invention will be described.

In this embodiment, the apparatus comprises: a bed 106 including acarrier plate 108 for carrying a lying patent 109, a height adjustmentunit 107 for supporting the carrier plate 108 at a freely adjustableheight in a vertical Z direction, a common base 103 for supporting theheight adjustment unit 107 in a state of being movable in a horizontal Xdirection, and a head rest 101 for supporting a head portion 109a of thepatient 109 which is fixed to the common base 103; and a frame 104having a cylindrical bore 105 into which the patient 109 on the bed 106is positioned by moving in a horizontal X direction, and a gamma camera102 capable of rotating 360° around a circumference of the cylindricalbore 105 to collect the tomographic image data. The gamma camera 102 hasan effective view field vf in the X direction which is narrower than itsfull width, and is capable of collecting tomographic image data onlywithin this effective view field vf. The collected tomographic imagedata are subsequently reconstructed into the multi-slice tomographicimages by using the signal processings, and the reconstructedtomographic images are displayed on a display device for medicaldiagnostic use. Here, the tomographic images can cover only thoseregions of the patient which are located within the effective view fieldvf of the gamma camera 102.

A front end 103a of the common base 103 facing the frame 104 isinitially located at a position a.sub.φ before the imaging operation,and after the patient 109 is positioned on the bed 106, the bed 106 ismoved in the horizontal X direction by a distance c.sub.φ such that thefront end 103a of the common base 103 is moved to a position a₁, while afront end 101a of the head rest 101 which is initially located at aposition b.sub.φ is also moved along with the common base 103 in thehorizontal X direction into the cylindrical bore 105 of the frame 104.Here, the front end 101a of the head rest 101 enters the effective viewfield vf of the gamma camera 102 as it passes a position b₁ located at adistance d.sub.φ away from the initial position b.sub.φ and is movedfurther to a position b₂ located inside the effective view field vf ofthe gamma camera 102 at which the imaging operation is carried out.

Therefore, a range of positions located between the positions b₁ and b₂which is equal to a length e.sub.φ =c.sub.φ -d.sub.φ is going to belocated within the effective view field vf of the gamma camera 102 inthis apparatus.

Accordingly, the apparatus further includes an indication marking 110 ofa length e.sub.φ attached on a side of the head rest 101 from the frontend 101a to a position 101b, which indicates this range that can belocated within the effective view field vf of the gamma camera 102. Thisindication marking 110 can be formed in any easily recognizableappearance such as a printed line, a colored tape, or a plateattachment.

Thus, in this embodiment, the accurate positioning of an imaging targetportion of the patient 109 within the effective view field vf of thegamma camera 102 can be achieved by a single positioning operation ofsimply adjusting the position of the patient 109 on the bed 106 withrespect to the indication marking 110 before the patient 109 is movedinto the imaging position inside the cylindrical bore 105 of the frame104, and the bed 106 carrying the patient 109 can be moved toward theframe 104 only after the accurate positioning of the patient 109 isascertained. Consequently, there is no need for frequent and cumbersomere-positioning of the patient 109 in this apparatus.

Referring now to FIG. 8, a second embodiment of a medical imagingapparatus according to the present invention will be described.

In this embodiment, the apparatus comprises: a bed 206 including acarrier plate 208 for carrying a lying patient 209 in a state of beingmovable in a horizontal X direction, a height adjustment unit 207 forsupporting the carrier plate 208 at a freely adjustable height in avertical Z direction, a common base 203 for fixedly supporting theheight adjustment unit 207; and a frame 204 having a cylindrical bore205 into which the patient on the bed 206 is positioned by moving in ahorizontal X direction, and a gamma camera 202 capable of rotating 360°around a circumference of the cylindrical bore 205 to collect thetomographic image data. The gamma camera 202 has an effective view fieldvf in the X direction which is narrower than its full width, and iscapable of collecting tomographic image data only within this effectiveview field vf. The collected tomographic image data are subsequentlyreconstructed into the multi-slice tomographic images by using thesignal processings, and the reconstructed tomographic images aredisplayed on a display device for medical diagnostic use. Here, thetomographic images can cover only those regions of the patient which arelocated within the effective view field vf of the gamma camera 202.

A front end 208a of the carrier plate 208 facing the frame 204 isinitially located at a position a.sub.φ before the imaging operation,and after the patient is positioned on the bed 206, the bed 206 can bemoved in the horizontal X direction by a distance c.sub.φ to a positiona₂. Here, the front end 208a of the carrier plate 208 enters theeffective view field vf of the gamma camera 202 as it passes a positiona₁ located at a distance d.sub.φ away from the initial position a.sub.φ.

Therefore, a range of positions located between the positions a₁ and a₂which is equal to a length e.sub.φ =c.sub.φ -d.sub.φ is going to belocated within the effective view field vf of the gamma camera 202 inthis apparatus.

Accordingly, the apparatus further includes an indication marking 210 ofa length e.sub.φ attached on a side of the carrier plate 208 from thefront end 208a to a position 208b, which indicates this range that canbe located within the effective view field vf of the gamma camera 202.This indication marking 210 can be formed in any easily recognizableappearance such as a printed line, a colored tape, or a plateattachment.

Thus, in this embodiment, the accurate positioning of an imaging targetportion of the patient within the effective view field vf of the gammacamera 202 can be achieved by adjusting the position of the patient onthe bed 206 with respect to the indication marking 210 before thepatient is moved into the imaging position inside the cylindrical bore205 of the frame 204, and the carrier plate 208 carrying the patient canbe moved toward the frame 204 only after the accurate positioning of thepatient is ascertained, as in the first embodiment described above.

Now, in the above embodiments of a medical imaging apparatus, the easilyand accurately readable indication of the height of the carrier platewithout a complicated configuration and an incresed cost can be providedby constructing the bed as in the following two embodiments.

Referring now to FIGS. 9(A) and 9(B), a first embodiment of a bed for amedical imaging apparatus according to the present invention will bedescribed.

In this embodiment, the bed comprises a base 301 having a lower rail 303along an X direction; an upper frame 302 having a carrier plate 302amovable in the X direction on an upper surface, and an upper rail 304running parallel to the lower rail 303 along the X direction on a lowersurface; and a pair of mutually crossing links 305 and 306 forsupporting the upper frame 302 over the base 301.

As shown in FIG. 9(A), the links 305 and 306 are held to be intersectingat a common pivot axis 307, where an upper end of the link 305 isrotatably fixed to an upper fixed axis 309 located at one end of theupper rail 304 and a lower end of the link 306 is rotatably fixed to alower fixed axis 308 located at one end of the lower rail 303, while alower end of the link 305 is rotatably connected to a lower slidableaxis 310 located near the other end of the lower rail 303 throughrollers 304b and an upper end of the link 306 is rotatably connected toan upper slidable axis 311 located near the other end of the upper rail304 through rollers 304a.

The bed also includes a cylinder 312 connected between the links 305 and306 on one side of the common pivot axis 307 such that the height of theupper frame 302 supported by the links 305 and 306 can be raised by theextension of the cylinder 312 in which case the lower and upper slidableaxes 310 and 311 slide towards the lower and upper fixed axis 308 and309 to raise the upper frame 302, or lowered by the contraction of thecylinder 312 in which case the lower and upper slidable axes 310 and 311slides away from the lower and upper fixed axis 308 and 309 to lower theupper frame 302.

In addition, as shown in detail in FIGS. 10(A), 10(B), and 10(C), thebed also includes an arm member 318 extending in the X direction whichis connected with the lower slidable axis 310 through a bearing member317. The arm member 318 has a pointer support section 318a extendingover the lower rail 303 in a Y direction on an end of which a pointer316 pointing upwards is attached, and rollers 319 for supporting the armmember 318 on the base 301 at a position near the pointer supportsection 318a. Thus, as the lower slidable axis 310 slides in the Xdirection, the pointer 316 on the arm member 318 moves along the Xdirection for the same distance.

The bed further includes a cover 314 for covering over the pointer 316on the arm member 318 which has a window 314a located directly above thepointer 316 such that the pointer 316 can be seen through the window314a, and a scale cover 315 attached on the cover 314 which has atransparent region at least over the window 314a and a scale markings Mfor indicating the height of the carrier plate 302a on the upper frame302 corresponding to the position of the pointer 316 in the X direction.

In this bed, by controlling the cylinder 312 from a control panel (notshown), the height of the upper frame 302 supported by the links 305 and306 can be raised by the extension of the cylinder 312 in which case thelower and upper slidable axes 310 and 311 slide towards the lower andupper fixed axis 308 and 309 to raise the upper frame 302, or lowered bythe contraction of the cylinder 312 in which case the lower and upperslidable axes 310 and 311 slides away from the lower and upper fixedaxis 308 and 309 to lower the upper frame 302. Then, as the lowerslidable axis 310 slides in the X direction, the pointer 316 on the armmember 318 moves along the X direction for the same distance, so that byreading the scale markings M on the horizontally provided scale cover315 pointed by the pointer 316, the height of the carrier plate 302a onthe upper frame 302 can be read off easily and accurately, withoutrequiring a complicated configuration in the bed or a cumbersomeoperation to the operator. Also, because the indication of the height ofthe carrier plate 302a is provided on a horizontal plane, it is readilypossible in this bed to lower the carrier plate 302a as low asconsidered preferable by many operators nowadays.

Referring now to FIGS. 11(A) and 11(B), a second embodiment of a bed fora medical imaging apparatus according to the present invention will bedescribed.

In this embodiment, the bed comprises a base 401; a lower support frame424 fixed on the base 401; an upper frame 402 having a carrier plate402a movable in the X direction on an upper surface; an upper supportframe 423 attached to a lower surface of the upper frame 402, which ismovable in the Z direction with respect to the lower support frame 424such that the height of the carrier plate 402a can be changed; and alink 421 having one end rotatably attached to one side of the uppersupport frame 423 through a shaft 426 and a bearing member 427 while theother end is equipped with rollers 425 for freely rolling on the base401 in the X direction and a pointer 422 functioning as a rotationalaxis of the rollers 425.

The bed further includes a cover 414 for covering over the pointer 422having a window (not shown) located directly above the pointer 422 suchthat the pointer 422 can be seen through the window, and a scale cover415 attached on the cover 414 which has a transparent region at leastover the window of the cover 414 and a scale markings M for indicatingthe height of the carrier plate 402a on the upper frame 402corresponding to the position of the pointer 422 in the X direction.

In this bed, by controlling the upper support frame 423 from a controlpanel (not shown), the height of the upper frame 402 can be raised orlowered. Then, as one end of the link 421 is also raised or loweredalong with the shaft 426 and the bearing member 427, the other end ofthe link 421 rolls on the base 401 such that the pointer 422 moves alongthe X direction. Thus, by reading the scale markings M on thehorizontally provided scale cover 415 pointed by the pointer 422, theheight of the carrier plate 402a on the upper frame 402 can be read offeasily and accurately, without requiring a complicated configuration inthe bed or a cumbersome operation to the operator. Also, because theindication of the height of the carrier plate 402a is provided on ahorizontal plane, it is readily possible in this bed to lower thecarrier plate 402a as low as considered preferable by many operatorsnowadays.

It is to be noted that the embodiments described above can be realizedin any medical imaging apparatus of a type in which a patient on a bedis to be moved into a view field of a signal detector located inside aframe such as a SPECT apparatus, an X-ray CT apparatus, and a gammacamera apparatus.

Besides these, many modifications and variations of the aboveembodiments may be made without departing from the novel andadvantageous features of the present invention. Accordingly, all suchmodifications and variations are intended to be included within thescope of the appended claims.

What is claimed is:
 1. A medical imaging apparatus for obtaining images of an imaging target portion of a patient from image data collected from the patient, comprising:signal detector means for collecting the image data, having a limited effective view field located inside a frame; carrier means for carrying the patient from outside of the frame to inside of the frame in order to place the imaging target portion of the patient within the limited effective view field of the signal detector means; and indication marking means, attached on the carrier means, for indicating a range on the carrier means which can be located within the limited effective view field of the signal detector means which is visible while the carrier means is located outside of the frame.
 2. The apparatus of claim 1, wherein the carrier means includes a head rest portion for supporting a head portion of the patient and the indication marking means is attached on the head rest portion of the carrier means.
 3. The apparatus of claim 1, further comprising:height adjustment means for adjusting a height of the carrier means by moving the carrier means in a vertical direction; and height indicator means for indicating the height of the carrier means adjusted by the height adjustment means on a scale provided on a horizontal plane.
 4. The apparatus of claim 3, wherein the height indicator means includes:means for converting a vertical motion of the height adjustment means to move the carrier means in the vertical direction into a corresponding horizontal motion; and pointer means, connected with the converting means, for indicating the height of the carrier means by pointing the scale and changing a horizontal position with respect to the scale according to the corresponding horizontal motion.
 5. The apparatus of claim 4, wherein the pointing means comprises a horizontally slidable member carrying out the corresponding horizontal motion, and the converting means comprises a link which is rotatably connected to a vertically moving part of the height adjustment means on one end and to the horizontally slidable member on another end.
 6. A medical imaging apparatus for obtaining images of an imaging target portion of a patient from image data collected from the patient, comprising:signal detector means for collecting the image data, having a limited effective view field located inside a frame; carrier means for carrying the patient into the frame in order to place the imaging target portion of the patient within the effective view field of the signal detector means; height adjustment means for adjusting a height of the carrier means by moving the carrier means in a vertical direction; and height indicator means for indicating the height of the carrier means adjusted by the height adjustment means on a scale provided on a horizontal plane.
 7. The apparatus of claim 6, wherein the height indicator means includes:means for converting a vertical motion of the height adjustment means to move the carrier means in the vertical direction into a corresponding horizontal motion; and pointer means, connected with the converting means, for indicating the height of the carrier means by pointing the scale and changing a horizontal position with respect to the scale according to the corresponding horizontal motion.
 8. The apparatus of claim 7, wherein the pointing means comprises a horizontally slidable member carrying out the corresponding horizontal motion, and the converting means comprises a link which is rotatably connected to a vertically moving part of the height adjustment means on one end and to the horizontally slidable member on another end.
 9. A system for obtaining a plurality of different tomographic images of radioisotopes given to an object, comprising:detector means having a two-dimensional detection area for detecting gamma rays coming from the radioisotopes; scanning means for causing a relative rotation around a rotation axis between the object and said detector means to obtain a plurality of projection data of a portion of said object corresponding to said detection area; reconstructing means for reconstructing the tomographic images from said plurality of projection data; carrier means for inserting said object into said scanning means along said rotation axis; and marking means disposed on said carrier means for visibly indicating a range along said rotation axis, where projection data are obtained when said object is sent to said scanning means by said carrier means. 